Lauter Tun Rakes

[Benchish]

This may seem like a stupid question to those who already know the answer but what do the rake arms in a lauter tun do?

The IBD notes that i'm looking at have basically the same description and picture (aside from the rakes in the picture) for both the mash/lauter tun and the lauter tun with no mention of the rakes serving any function.

Are they just to remix the mash after being pumped from the mash tun?
Or to help empty after everything else is done?

 

[bum]

My understanding is that they're for both mixing the mash and expelling spent grain.

Can't say I've ever seen someone using one on a HB scale though. I'm sure someone does and might post their experiences.

 

[hsb]

+1. See http://en.m.wikipedia.org/wiki/Lautering - Lauter Tun section.

Most Homebrewers use a single vessel for Mash/Lauter, less to clean, less to buy/build.
Are you thinking of making a separate Lauter Tun?

 

[Benchish]

Just trying to understand how/why they work and are included in a separate latter tun and not a mash/lauter tun.

Pumping to a separate lauter tun would free up a mash tun to go again, and that makes sense on a commercial scale but not on a home scale for most (there is always someone).

From wiki: "The brewer, or better yet an automated system, can raise and lower the rake arms depending on the turbidity (cloudiness) of the run-off, and the tightness of the grain bed"

what effect would the rakes have on turbidity? or bed tightness?

 

[jayse]

when the turbidity rises rakes go up when the bed tightens the rakes go down, the rakes enable and even sparging of all the grain and almost elliminates channelling through sections of the grain bed. Another benefit of a seperate lauter tun (and in some breweries more important then the fact you free up the mash tun sooner) is you are not mixing the mash on top of a false bottom which is not ideal.

 

[np1962]

Just trying to understand how/why they work and are included in a separate latter tun and not a mash/lauter tun.

Pumping to a separate lauter tun would free up a mash tun to go again, and that makes sense on a commercial scale but not on a home scale for most (there is always someone).

From wiki: "The brewer, or better yet an automated system, can raise and lower the rake arms depending on the turbidity (cloudiness) of the run-off, and the tightness of the grain bed"

what effect would the rakes have on turbidity? or bed tightness?

You're on the right track with the mash tun/lauter tun and being able to get a second mash underway sooner.
The idea of the rakes is that in the lauter tun has to do with the grain compacting and giving a stuck sparge.
Most lauter tuns have pressure sensors, one near the bottom of the bed and one higher up. By using the reading of the difference in the two pressures and then using the rakes at varying speeds you are able to prevent sticking.
In most cases rakes are unnecessary in a homebrew setup as you just don't have the weight of grain in the tun. Not to say you can't get a stuck sparge but it's easier to fix with <15kg grain as compared to >300kg even on a small commercial setup.
You can raise the rake to have a slightly thicker filter bed if you have a turbid run off.
Nige

 

[The Scientist]

A lot of commercial breweries mash tuns double as their boil kettle, hence the need to transfer the mash to a lauter tun. So the wort can be drained back in to the cleaned out kettle.

The rakes are adjustable in height and are used to keep the grain bed from compacting and also assist with flow of the wort from the grains. At the time of removing the spent grain, some rakes are designed to be able to be reversed and assist in cleaning out the lauter tun.

 

[MHB]

There are two types of equipment we could be talking about
First is mixing paddles, these are just used in large tuns to keep everything at an even temperature, remember that you can only really add heat from the sides and bottom of the tun and that it would take a long time for the heat to travel through the mash, mixing keeps the mash homogeneous.
Second are rakes
These are really the providence of big commercial brewing, they can serve as mixers but their main job is to open up the grain bed to speed up lautering, which in a modern High Speed Lauter can take over 1 and 1/2 hours (and home brewers often wonder why big brewers get such high efficiency). The individual elements of the rake are called knives, wiggles in the knives is to stop channelling. They are really high end brewing technology and probably not a lot of use to home brewers as they require very sophisticated computer control to really get the most out of them.
Dam sexy but seen some with Teflon toes that when it comes time to clean out the tun, by reversing the rotation all the knives turn side on and scrape out the malt, didnt leave much behind either.
Here is a quick scan from Kunze that gives a good idea of their operation.
Mark
Ah I see Nige has said pretty much the same thing
m
View attachment 52045

 

[DUANNE]

might seem a stupid question but, from what ive seen of commercial mash sytems woudnt the raking and sparging from a height above the main mash introduce oxidation?

 

[Thirsty Boy]

In a HB situation, you can achieve much the same thing by taking a big arse kitchen knife and "cutting" your grain bed in a criss cross fashion. keep the knife a cm or two from touching the fb, and cut a diamond pattern into the grain bed with gaps about 1cm between the cuts. it can loosen up a stuck sparge and even out the flow through a tun thats prone to channeling, especially if the tun is prone to channeling down the walls. It will lessen your wort clarity because it interferes with your grain bed, and if you go too deep or too enthusiastically, you might have to repeat your vorlauff to re-set your bed. I also occasionally stab holes into my grain bed with a knitting needle - doing much the same job as cutting the bed. Lightly cutting/poking your grain bed can be particularly helpful if you tend to develop a fine layer of "mud" like sediment on top of your mash - which can almost seal the surface to liquid and cause the mash to pull down and compact onto the FB, or just to channel the wort down the walls of the tun. Poke a few holes and watch in amazement as your wort starts to actually flow through your grain bed

Most HB tuns are more deep and narrow though, and you get a more "floating" grain bed - lauter tuns tend to be wider, flatter and have the grain bed sitting more firmly on the plates - the increased surface area increases the potential flow rate, and a finer crush increases mash speed and efficiency - but you need the rakes to stop it all turning into a stuck mash nightmare (still happens sometimes anyway)

Quite a few "mash tuns" will have what look like rakes, but really only serve to do a little initial mixing and spreading out of the grain bed - they dont necessarily act during the lauter at all - then maybe they turn perpendicular and scrape all the grain to dump holes on the edge of the tun during the grain out. Its not really practical to shovel out multiple ton grain bills.

 

[Thirsty Boy]

might seem a stupid question but, from what ive seen of commercial mash sytems woudnt the raking and sparging from a height above the main mash introduce oxidation?

yes, it does. Its a trade off.

 

[Wasabi]

might seem a stupid question but, from what ive seen of commercial mash sytems woudnt the raking and sparging from a height above the main mash introduce oxidation?

Extract is more valuable at those volumes, at least for bigger breweries, who have oxidation under tight control anyway. Plus the debate around the damage preboil oxygen does will rage for eons to come...